Most incorporated physicians and dentists spend real effort deciding what to invest their corporate surplus in — index funds, individual equities, GICs, private placements. Far fewer spend any time deciding where those different investments should sit, or what type of income they generate once inside the corporation. That second question, known as asset location, can be worth more to an incorporated professional over a decade than another year of tinkering with fund selection.
This is a foundational piece of financial planning for doctors and dentists that rarely gets discussed outside a year-end tax meeting — by which point most of the flexibility to act on it has already passed.
Why Your Corporation Taxes Investment Income Differently by Type
A professional corporation (PC) doesn’t apply one flat tax rate to investment returns. The Canada Revenue Agency taxes four categories of corporate investment income differently:
- Interest and foreign income — taxed at the highest rate inside the corporation, with a portion refundable only once dividends are paid out to you personally.
- Canadian eligible dividends — benefit from the dividend tax credit and are generally the most tax-efficient income type to hold inside a PC.
- Foreign dividends — taxed similarly to interest, without the same dividend tax credit relief, and sometimes subject to foreign withholding tax before it even reaches the corporation.
- Capital gains — only half is taxable, with the taxable half added to a pool that determines how much passive income counts toward the small business deduction grind, while the non-taxable half flows into the Capital Dividend Account for future tax-free extraction.
Two portfolios with identical expected returns can produce very different after-tax outcomes for a corporation depending on which of these four buckets the income falls into.
The Mechanic Most Advisors Gloss Over: Refundable Dividend Tax on Hand
When your corporation earns interest, foreign income, or the taxable portion of a capital gain, a meaningful chunk of the tax paid isn’t gone for good — it lands in a notional account called Refundable Dividend Tax on Hand (RDTOH). Your corporation only recovers that refund when it pays a taxable dividend out to you personally, at a fixed recovery rate per dollar of dividend paid.
The practical implication: RDTOH creates a built-in incentive to eventually pay yourself dividends from a corporation holding interest-bearing or foreign investments, rather than letting the cash accumulate indefinitely. Professionals who reinvest corporate surplus for decades without ever triggering a dividend are effectively leaving that refund on the table — sometimes for the life of the corporation.
A Practical Framework for Locating Assets Inside the PC
Rather than defaulting every account to an identical, generically “balanced” portfolio, a more deliberate structure typically looks like this:
- Hold Canadian dividend-paying equities inside the corporation where possible, since eligible dividends are the most efficiently taxed income type at the corporate level.
- Push interest-heavy and foreign-income holdings toward personal or registered accounts (TFSA, RRSP) where they escape the corporate RDTOH mechanics entirely.
- Use the corporation for buy-and-hold, low-turnover positions so capital gains realization — and the resulting hit to your passive income threshold — stays within your control rather than being dictated by fund turnover.
- Revisit the mix annually, particularly after a year with unusually high realized gains, since that affects both RDTOH balances and how close the corporation sits to the $50,000 passive income threshold that begins eroding the small business deduction.
None of this replaces a properly diversified portfolio — it’s a layer on top of it, designed to reduce the tax friction between what your investments earn and what actually ends up compounding for you.
Where This Connects to the Passive Income Grind
Asset location decisions don’t happen in isolation. A corporation earning primarily eligible dividends and deferred capital gains will typically generate less “adjusted aggregate investment income” in a given year than an identical portfolio weighted toward interest and foreign income — which matters directly for how much of your $500,000 small business limit survives intact. Coordinating asset location with this threshold is worth a dedicated conversation with your advisor rather than a single line item.
A Research-Backed Note on What You Hold, Not Just Where
Structuring for tax efficiency is only useful if the underlying portfolio itself is sound. Physicians and dentists sometimes lean toward concentrated positions in pharmaceutical or biotech names, reasoning that their clinical background gives them an edge in reading the sector. Decades of empirical research from Nobel laureate Eugene Fama point the other way: prices in liquid public markets tend to reflect available information faster than any individual investor, clinical training included, can consistently act on. A broadly diversified, low-cost portfolio built around known, compensated risk factors has historically been a more reliable engine for corporate surplus than a handful of familiar-sounding tickers — asset location optimizes the tax wrapper, but diversification protects what’s inside it.
The Bottom Line
Where you hold each type of investment inside your professional corporation is not a minor detail — it directly affects how much of your corporate surplus survives taxation at every stage, from annual RDTOH refunds to your long-term small business deduction eligibility. Getting the structure right once tends to compound in your favour for as long as the corporation exists.
Ready to review how your corporate investment account is structured? Book a private consultation with the team at financialadvice.ca or call at 587 718 8001 and let’s make sure your corporate surplus is working as efficiently as your practice does.
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